91 Ls Doesn't Start After 20 Min. Drive, However

[blessed]

91 LS with 225k runs great, however, it doesn't start after driving it for a while. Letting it sit seems to fix the problem (that is until it's driven again for a while). After sitting for at least 1 hour it will start with no problem.

The car will turn over, but doesn't seem to be getting fuel so it just turns over and over without starting. A short drive (under 15 min) and the car will start again without a problem.

Is this a vapor lock or is the Feul Pump going bad or what??????

Thanks in advance for your help!

s

[landar]

Well blessed, your Lexus fuel saver module is kicking in to help save you money. Whenever gas prices hit

these high levels, your car makes you wait a least one hour to keep you from unnecessary road trips. Kinda

like the search flood control used on this board....... Kidding! :whistles:

So, there are quite a few unanswered questions in my mind: Does your car run fine for hours on end if you

just keep driving? How hot is your local? What kinda fuel are you running? Does she crank robustly or sluggish after hot?

Vapor lock used to occur on older cars with fuel pumps that 'pulled' gas from the tank. Today's cars generally have

tank mounted pumps which 'push' the gas to the engine, so to my understanding, vapor lock is no longer an issue.

If'n it were my Lex, I would probably want to determine if the problem were fuel or spark. Even though it seems like

fuel, dont rule out the other. To that end, when it wont start, I would check for spark. If it had spark, I would check the

fuel pressure or maybe worse yet, be tempted to squirt a little engine starter fluid down the throttle body (I know, I know,

bad for the old engine). But thats just me. If it starts right up, you gotta a fuel delivery problem.

[larryp]

I agree w/ landar's recommendations. i'd probably start by pulling the plugs and checking them when it won't start. Look for "wet" condition - plugs fouled by too much fuel. Could be once it has sat for a while the plugs are drying out enough to fire. Just my $.02.

[leximus]

I had a similar problem, but thought it was my alternator. Turned out the positve batery cable was not completely secured. Hmmm...

[blessed]

Thanks for your ideas guy's!

The car runs like new after it starts. This has been happening most of the summer and it's been a somewhat hot and dry one in Nor Cal (Sacramento).

Thanks for ruling out the Vapor Lock idea and I'll pull one of the plugs the next time it happens when at home. I'm running regual octane fuel (87) for the most part. I'll also purchace a can of starter fluid and check my battery connections.

I'll keep you guys posted.

Thanks again for your input.

Blessed

[Mickeyls400]

My car is doing the same thing for about a month, I thought it was the idle control but its not. Any ideas because now it won't fire?

[mrfixit]

My '93 LS400, with over 200k miles, just started doing the same thing. After driving about ten miles yesterday, it quit suddenly. After sitting for an hour, it started and ran fine for about five miles, then quit again. After sitting overnight, it started and ran long enough to get home, another five miles away.

Once it dies, it cranks over fine, just won't start. My strong suspicion is that the problem is electrical, something gets hot then stops working. Tomorrow, I'm going to begin by checking the battery connections as suggested above. Next will be the coils, of which there are two. Seems like I had a similar problem once before and it was one of the coils.

[alsalih]

These symptoms are related to the fuel pump failing. That’s exactly what it starts doing before eventually going out completely. Make sure you also replace the fuel filter after doing this job.

[mrfixit]

Is there any way to test the fuel pump in this condition? Will there be any stored computer code?

[alsalih]

This would not store a code. You could try a fuel pressure test however there is the possibility that it might actually still be within specifications and lead you to believe that it’s ok. The simplest thing to do is to listen for the fuel pump “buzz” when you turn the ignition key from position 1 to 2 without starting. When the car fails to start after being warm you should notice that when turning the ignition key you will not hear the fuel pump buzz. Actually, with the LS you might almost want to have someone turn the ignition while you stick your head in trunk listening for the fuel pump sound as it’s so quiet you might not hear it in the cabin. Anyway, there is the remote possibility that your fuel pump relay is bad, so check that first just to make sure, however those hardly ever fail on the LS so I really doubt it would the cause.

[mrfixit]

Just as a follow-up, I cleaned and re-attached my positive battery terminal. The post was oxidized and I don't think it was getting a good connection.

I also found a crack in the accordion section of the air intake tube, which I repaired with duct tape (black of course). After driving for quite a while the engine never died. It seems like my problem may be corrected. If the problem reoccurs, I'll follow-up again.

[poetali]

My car is doing the same thing for about a month, I thought it was the idle control but its not. Any ideas because now it won't fire?

have you fixed your problem

[mrfixit]

Previously, I posted that after cleaning the battery connections my problem seemed to be fixed. Not so. This is one of those intermittent problems that is so hard to diagnose.

After cleaning the battery connections, the car ran fine for two days, then died again. And, again, after sitting overnight, started right up, ran for about five miles, then quit.

Still thinking it was an electrical problem, I purchased and installed a new battery. No joy, problem persisted.

Following the recommendation of another poster above, I ordered a fuel pump and replaced that, only to have the problem continue. Fuel pump was not the problem (more on this below).

When the car would die, I sometimes would open the hood and tap on various components to see if something would shake loose (or shake into place), and indeed sometimes this would cause the car to start. I noticed that after tapping on the upper coil, the car started. Ah-ha! I remembered that when I replaced the coil a year ago, the locking connector cracked (like so many of them do on these cars). The connector is very hard to get to, but I was able to stick a screw driver in far enough to push the connector into the connection and the car started right up. When I wiggled the connector, the car died.

The wire from the wiring harness is very short for this connection, making it very difficult to keep it in place once the retaining clip breaks. I am going to have to come up with some way to make the connector stay in place better for a long-term fix. But for now, this has for sure fixed my problem.

On a different note, regarding the fuel pump. I bought a cheap one on eBay, for about $50 shipped. It was visibly much cheaper construction than the original one and noticeably louder in operation when connected to the battery for testing. However, once installed there was no noticeable noise, so I left it in for now, keeping the original just in case. For a car with over 200k miles I didn't think it was a bad choice buying the cheap fuel pump on eBay, when all of the local parts houses wanted over $200 for a replacement pump.

This forum has been a great help to me on many occasions, so hope this helps someone else down the road.